Perform many different routines using small objects like Coins or Rings! Borrow a coin, and have it marked, then you make it vanish! Display a painted box thats tied closed with a length of red ribbon. Have them untie the ribbon and open the lid, maybe their coin is inside?
Inside this Box is a 2nd Box tied with ribbon! They untie the ribbon on the 2nd Box, to find a 3rd Box inside! Inside the 3rd Box is a tiny wooden box! And inside this tiny box is their marked coin!